1. Technical Field
The invention relates generally to semiconductor device fabrication, and more particularly, to a transistor structure having an interconnect to a side of a diffusion, which allows electrical connection to the diffusion without interrupting a stress liner film, and related methods.
2. Background Art
The application of stresses to field effect transistors (FETs) is known to improve their performance. When applied in a longitudinal direction (i.e., in the direction of current flow), tensile stress is known to enhance electron mobility (or n-channel FET (NFET) drive currents) while compressive stress is known to enhance hole mobility (or p-channel FET (PFET) drive currents). One way to apply such stresses to a FET is the use of intrinsically-stressed barrier silicon nitride liner films. For example, a tensilely stressed silicon nitride liner film may be used to cause tension in an NFET channel while a compressively-stressed silicon nitride liner film may be used to cause compression in a PFET channel. Accordingly, a dual/hybrid liner film scheme is necessary to induce the desired stresses in an NFET and adjacent PFET.
Stress liner films are now an integral part of leading edge high-performance technologies, in particular silicon-on-insulator (SOI) technologies. These films can provide performance gains on the order of the projected gains for an entire technology node. However, stress liner films suffer when structures such as local interconnects between gates interrupt the stress liner film. In particular, the interruptions dilute the mobility/performance enhancement of the stress liner films where they are most effective—close to the gate. Typically, the closer the contacts are the worse the effect is to the performance. One approach to this problem is to reduce the number of contacts. This solution, however, limits design possibilities and increases contact resistance. In other approaches, a silicide strap or a wire using higher levels of metal wiring is used. These approaches unfortunately result in higher resistance.
In view of the foregoing, there is a need in the art for an improved way to electrically connect an interconnect to a diffusion, especially where stress liner films are implemented.